House mouse (Mus musculus) the common mouse is one of the species of the genusMus. Often, it is just called a mouse. It is a small rodent. In most parts of the world, they live close to humans. Laboratory mice are types of house mice and are some of the most important organisms used for research in biology and medicine. They are the most commonly used laboratory mammal for experiments.

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Description

They are quite small, but are not the smallest mammals. House mice have an adult body length (nose to base of tail) of 7.5–10 cm (3.0–3.9 in) and a tail length of 5–10 cm (2.0–3.9 in). The weight is typically 10–25 g (0.4–0.9 oz). In the wild they vary in color from light to dark agouti (light to dark brown). Selected strains of mice can be got in various other colours.

It is a small, scaly-tailed mouse with a distinct notch in the cutting surface of upper incisors (seen best in side view). Its hair short; ears moderately large and naked.

Physiology

The main problem of small mammals is their high surface to weight ratio: they have a big surface area for such a small mass. Since heat is radiated from the surface, they have adaptations to help them keep their temperature up to normal. They need to eat frequently, and live in areas where they are protected from the coldest weather. Easy access to high-quality vegetable food (such as grains) and a protected habitat helps them survive and multiply. That is why they are found in numbers living in human settlements.

Life cycle

A two-day-old mouse

Their life-span in the wild averages about a year. They are eaten by a variety of small carnivores, but they reproduce rapidly, so that keeps the numbers up. Females have 3–14 babies in a litter, and can have 5 to 10 litters a year. In good conditions, the mouse population rises quickly.

Habitat

Infestation of mice

Although not native to North America the house mouse, it was introduced accidentally to seaport towns. It is now widespread throughout the United States. It occurs either as a commensal or feral animal in practically all parts of the U.S.

As commensal animals, house mice live in close association with man – in his houses, outbuildings, stores, and other structures. Where conditions permit, feral mice may be found in fields, along watercourses, and in other places where vegetation is dense enough to hide them.

Behavior

Feeding

House mice usually run, walk, or stand on all fours, but when eating, fighting, or orienting themselves, they rear up on their hind legs with additional support from the tail - a behavior known as "tripoding". Mice are good jumpers, climbers, and swimmers, and are generally considered to be thigmotactic, i.e. usually attempts to maintain contact with vertical surfaces.

Mice are mostly crepuscular or nocturnal; they are averse to bright lights. The average sleep time of a captive house mouse is reported to be 12.5 hours per day. They live in a wide variety of hidden places near food sources, and construct nests from various soft materials. Mice are territorial, and one dominant male usually lives together with several females and young. Dominant males respect each other's territories and normally enter another's territory only if it is vacant. If two or more males are housed together in a cage, they often become aggressive unless they have been raised together from birth.

House mice primarily feed on plant matter, but are omnivorous. They eat their own faeces to acquire nutrients produced by bacteria in their intestines. House mice, like most other rodents, do not vomit.

Mice are generally afraid of rats which often kill and eat them, a behavior known as muricide. Despite this, free-living populations of rats and mice do exist together in forest areas in New Zealand, North America, and elsewhere. House mice are generally poor competitors and in most areas cannot survive away from human settlements in areas where other small mammals, such as wood mice, are present. However, in some areas (such as Australia), mice are able to coexist with other small rodent species.

Mice and humans

House mice usually live in proximity to humans, in or around houses or fields. Originally native to Asia (probably northern India), they spread to the eastern Mediterranean about 13,000 BC, only spreading into the rest of Europe around 1000 BC. This time lag is thought to be because the mice require agrarian human settlements above a certain size. They have since been spread to all parts of the globe by humans.

Many studies have been done on mouse phylogenies to reconstruct early human movements. For example, one study suggests the possibility of a previously unsuspected early link between Northern Europe and Madeira on the basis of the origin of Madeiran mice. House mice were thought to be the primary reason for the taming of the domestic cat.

An individually ventilated and sealed cage for laboratory mice

The first written reference to mice kept as pets occurs in the Erya, the oldest extant Chinese dictionary, from a mention in an 1100 BC version. Human domestication led to numerous strains of "fancy" or hobby mice with a variety of colours and a docile temperament. Domestic varieties of the house mouse are bred as a food source for some carnivorous pet reptiles, birds, arthropods, and fish. The effects of domestication can be rapid, with captive-reared mice differing in boldness and activity patterns compared to wild-caught mice after 4-5 generations in recent research.

When infesting homes, house mice may pose a risk of damaging and compromising the structure of furniture and the building itself. They gnaw various materials to file down their growing teeth and keep the length under control. Common damage includes gnawed electrical wires, marks on wooden furniture and construction supporting elements, and textile damage.

Images for kids

A two-week-old fancy mouse, just about to open its eyes

In both agricultural and urban environments house mice are often preyed upon by the domestic cat.

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